Surface grafting on poly(ethylene terephthalate) track‐etched microporous membrane by activation with trifluorotriazine: Application to the biofunctionalization with GRGDS peptide

A two‐step wet chemistry protocol has been developed for the surface derivatization of poly(ethylene terephthalate) (PET) track‐etched membrane used as cell culturing support, that is, (a) activation by trifluorotriazine (1 M in acetonitrile (ACN), 30 °C, 3 h); (b) coupling to amine‐terminated molecules, namely 3,5‐bis(trifluoromethyl)benzylamine ((F)Tag), (L)‐4,5‐[³H]‐lysine, and Gly‐Arg‐Gly‐Asp‐Ser (GRGDS) pentapeptide (10^?3 M in PB‐ACN, 1:1 (v/v), 20 °C, 17 h). The grafting rates determined by X‐ray photoelectron spectroscopy, from the F/C and N/C atomic ratios, are in the range of 100–140 pmol/cm² (apparent surface), whereas the liquid scintillation counting assays give higher values (180–230 pmol/cm²) corresponding to the open surface reactivity. PET‐g‐(F)Tag is reasonably stable under two usual sterilization conditions of biomaterials, that is, steam heating at 121 °C and γ‐irradiation at 25 kGy. On the other hand, PET‐g‐GRGDS is found to be stable only under ionization radiation (84% of remaining peptide molecules), but damaged in a large extent by the autoclave treatment (23% of remaining peptide molecules). The surfaces of the sterilized PET and PET‐g‐GRGDS samples have been characterized by water contact angle measurement and by atomic force microscopy analysis in air and under water. Comparatively to the corresponding nonsterilized surfaces, γ‐irradiated surfaces are slightly more hydrophilic and also slightly more rough and jagged. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 195–208, 2010     

Development of a simulation model for dynamic derailment analysis of high-speed trains

The running safety of high-speed trains has become a major concern of the current railway research with the rapid development of high-speed railways around the world.The basic safety requirement is to prevent the derailment.The root causes of the dynamic derailment of highspeed trains operating in severe environments are not easy to identify using the field tests or laboratory experiments.Numerical simulation using an advanced train–track interaction model is a highly efficient and low-cost approach to investigate the dynamic derailment behavior and mechanism of high-speed trains.This paper presents a three-dimensional dynamic model of a high-speed train coupled with a ballast track for dynamic derailment analysis.The model considers a train composed of multiple vehicles and the nonlinear inter-vehicle connections.The ballast track model consists of rails,fastenings,sleepers,ballasts,and roadbed,which are modeled by Euler beams,nonlinear spring-damper elements,equivalent ballast bodies,and continuous viscoelastic elements,in which the modal superposition method was used to reduce the order of the partial differential equations of Euler beams.The commonly used derailment safety assessment criteria around the world are embedded in the simulation model.The train–track model was then used to investigate the dynamic derailment responses of a high-speed train passing over a buckled track,in which the derailmentmechanism and train running posture during the dynamic derailment process were analyzed in detail.The effects of train and track modelling on dynamic derailment analysis were also discussed.The numerical results indicate that the train and track modelling options have a significant effect on the dynamic derailment analysis.The inter-vehicle impacts and the track flexibility and nonlinearity should be considered in the dynamic derailment simulations.     

Complex Oscillations Revisited

The problem of applying some approaches to approximate solutions and the asymmetry of closed phase trajectories in some domain of parameters are examined__________Translated from Prikladnaya Mekhanika, Vol. 41, No. 2, pp. 81–90, February 2005.     

单板机在气轨实验中的应用

本文研究了如何利用TP－801单板机来改进气垫导轨实验，使数据的采集、存储和打印能够一次完成，并给出了相应的电路图。     

Location of rectilinear center trajectories

A rectilinear center trajectory is a polygonal line consisting only of horizontal and vertical segments which minimizes the maximum distance tom given points in the plane. In this paper a polynomial time geometric procedure, to find a center trajectory subject to the number of bends, is presented. When the polygonal is constrained on the extreme segments a modified algorithm is designed.     

New approach for describing transient pressure response generated by horizontal wells of arbitrary geometry

This paper is aimed at developing a methodology for studying the transient pressure behavior of horizontal wells with any curvilinear trajectory in an isotropic/anisotropic arbitrarily shaped reservoir. This methodology employs generalized functions to represent the tortuous horizontal well. A particular way of removing the singularities involved in the partial differential equation is based on reducing the original problem to the conventional solution of the homogeneous diffusivity equation under any given initial and boundary conditions. The Green function method and any standard numerical technique are combined in a single computational strategy to obtain the transient pressure response generated by a curved and twisted horizontal well in reservoirs with irregular boundaries. Analytical methods can be also used, whenever possible, to solve the reduced problem. This proposal can be easily broadened to analyze the performance of the pressure transient of any kind of reservoir sources or sinks that can be modeled using generalized functions. Some models are presented.     

Dynamic models relating processing parameters and melt track width during laser marking of clay tiles

This paper describes two dynamic models relating processing parameters and melt pool width during laser marking/engraving of clay tiles using a high-power diode laser. The models were determined by process identification techniques and were validated with a PI algorithm. The output variable considered for the laser clay tile marking process was melt pool width, measured by using a fast CCD recording system and analysed with an image-processing software. The input quantities investigated were laser power and traverse speed. Reasonable agreements between the measured data and the model outputs were achieved. Errors less than 1.3 μm of the melt pool width for the operating points were found. On the basis of these models a simple PI-controller was designed and tuned to guarantee zero steady-state error in case of an absorptivity disturbance.     

Characterization of nuclear tracks by positron annihilation and gas permeation

The application of polymeric membrane in combination with metallic films can be used for gas purification in particular for hydrogen where the molecular size is very small. The affinity of hydrogen to certain metals assists the flow of hydrogen, although it restricts the permeation of other gases. However, the flow rate is very small in dense membranes. Attempts have been made to generate nuclear tracks in polymeric membranes to control the gas flow. These tracks can be characterized by positron lifetime spectroscopy and gas permeation measurements. The long lifetime of ortho-positronium gives the estimate of size of the track-free volume of the order of 0.25 nm. The nuclear tracks can be modified by a chemical etching process. The chemical etching normally takes place from both sides of the membrane. When the etched pits from both sides meet, a rapid increase in gas permeation is observed. The size of the nano opening of the track has been observed for two different gases hydrogen and carbon dioxide, which have a molecular size of 0.2 and 0.4 nm, respectively.     

AFM method for investigation of irradiated polymers

Tracks of swift heavy ions (Xe and Bi) at the surface of polymer (PET) were studied using AFM and surface defects—cavities (for Xe) and hillocks with cavities on its top (for Bi) were found. Thermal behavior of these Bi-irradiated samples (during annealing from 70°C to 180°C) was investigated. It was found that low-temperature annealing does not change the shape of surface defects, while high-temperature annealing leads to slow disappearance of these defects.

Irradiation of a stack of ultra-thin PET films by fission fragments was carried out and some sheets were then investigated separately. Two types of defects, corresponding to two main types of incident fragments (according to average energy distribution) were found. The deep structure of a track was studied and the ranges for two types of fragments were estimated. The increase of area of destruction was found at the depth 10–12 μm, which may be associated with changing of mechanism of interaction of passing particle with polymer and the dominant role of nuclear interaction. The obtained results are supported by a model calculation.